Chemical Analysis of Milk and Its Products. 249 



tion (2 per cent.) are added. The mixture is then 

 shaken; if a dark violet color appears at once, the mUk 

 has not been heated, or at any rate not beyond 176° F. 

 If a sample of butter is to be examined, 25 grams are 

 placed in a small beaker and melted by being placed in 

 water of 60° C. The clear butter fat is poured off, and 

 the remaining liquid is diluted with an equal volume of 

 water. The mixture thus obtained is examined as in 

 case of milk. 



Guaiacum tincture has also been recommended for the 

 detection of pasteurized cream or milk; this solution is 

 easily obtained, keeps well, and is convenient to use 

 (McKay). 



295. Boiled milk. The preceding tests will serve to 

 distinguish between raw and boiled milk, and also to 

 ascertain if milk has been adulterated with diluted con- 

 densed milk. To what extent such an adulteration can 

 be practiced without being detected by this or similar 

 tests, has not been determined, but if a control test be 

 made at the same time with a sample of milk of known 

 purity, a small admixture of boiled (or diluted con- 

 densed) milk can doubtless be detected.^ 



296. Gelatine in cream. This method of adultera- 

 tion is sometimes practiced in the city cream trade, to 

 impart stiffness and an appearance of richness to the 

 cream. To detect the gelatine, a quantity of the sus- 

 pected cream is mixed with warm water, and acetic acid 

 is added to precipitate the casein and fat (1.5 cc. of 10 

 per cent.-acetic acid per 10 cc. of cream is sufficient). 



' See nlso Slats, Unters. landw. wlcht. Stoffe, p. 60. and Molkerel- 

 Ztg. (Illldeshelm), 1899, p. 67T. 



